The present invention relates essentially to a mixture-drawing internal combustion engine having an automatically controlled heating device arranged in heat exchange contact with an intake conduit for a fuel-air mixture. The heating device receives both cooling water diverted from a cooling water circulation system of the internal combustion engine and exhaust gases emitted from the internal combustion engine.
An internal combustion engine described in German Pat. No. 861,176 comprises a combined cooling water and exhaust gas heating system for an intake conduit of the internal combustion engine. In that heating system, automatic control is achieved by a deflection valve installed in a heating pipe carrying the exhaust gases, the deflection valve being actuated by a bimetallic spring. During idling of the internal combustion engine and at low speeds, the deflection valve directs the exhaust gases to a heating zone of the intake conduit; while at higher engine speeds, the exhaust gases are diverted directly into the exhaust system circumventing the heating zone of the intake conduit.
During the operation of heating systems of that type, it has been found that locating the deflection valve and its actuating mechanism within the heating pipe carrying the exhaust gases provides imperfect control of the heating device. More particularly, after some period of operation, the dirt and soot accompanying the exhaust gases are deposited on guides of the deflection valve, thereby disadvantageously hindering the proper operation thereof. Furthermore, the high temperature of the exhaust gases tends to cause operating difficulties which may result in the failure of the heating device.